This invention relates to under water cutting of steel walls or plates, and preferably the cutting of steel pilings. Heretofore, the methods for cutting steel underwater have been difficult to employ and the results thereof restricted. Oxy-hydrogen torches for this purpose have been provided for the introduction of compressed air into a surrounding sleeve in order to prevent the intrusion of water that would otherwise extinguish the flame; however cutting efficiently with that method is limited due to the excessive preheat time required, and only thin cuts can be made therewith, and without cutting through mud, scale, cement or rock etc.. Another cutting method involves striking an electric arc in the presence of oxygen introduced through the cutting rod, which works well with steel but not with non ferrous materials and other compositions such as concrete, rock, coral, etc.. Also, a good electric ground is often very difficult to attain.
An electrical development is the use of aluminum and/or magnesium rods within steel tube, used in steel cutting processes, with oxygen applied therethrough for oxidization. In the case of non-ferrous materials, the intense heat of burning crumbles the materials and the oxygen stream blows it away. Another development is the use of metal powders for intensifying heat and corrosive action. For example, mixtures of magnesium and iron dust support combustion in the presence of pure oxygen, but again with the use of a rod striking and electric arc. Such metal rods are self consuming in short lengths of time, which greatly shortens the cutting time. Furthermore, the use of electric arc cutting involves excessive down time because of the necessity to replace said rods so frequently; since such rods consume in 30 to 60 seconds. Therefore, it is a general object of this invention to provide a continuously operable method of cutting steel casings or plate underwater with a gas torch using powdered metal mixtures, without resort to electric arc rods that have been relied upon in the past.
Heretofore, it has been found to be difficult to attain sufficiently high preheat temperatures underwater, prior to discharge of the cutting agent such as pure oxygen, in order to perform cutting of steel plate such as that of casings. However, there are the aforesaid powdered metal mixtures that will raise the temperature of a flame considerably, but which are used sparingly because of their cost. Support for combustion of these powdered metals is the use of an oxidizer as a cutting agent. It is therefore an object of this invention to substantially raise preheat temperature in a cutting torch by providing the combustion of powdered metals, for example to raise the cutting zone temperature in excess of 4000.degree. F. and under which condition a cutting agent is discharged therewith for cutting the steel casing or plate. With the exothermic condition thus provided, this torch will now melt through mud, clay, corrosion scale and marine growths, while efficiently cutting steel and other metals on a continuing basis.
It is an object of this invention to provide an underwater gas cutting torch with at least three distinct gas supplies; a first pilot gas or ignition supply; a second preheat gas mixture or high temperature supply; and a third cutting agent supply. In practice, the first supply is a mixture of oxygen and hydrogen for the establishment of an under water pilot or igniter flame which may be continuous burning; and alternately a spark igniter can be used in lieu thereof. The second supply is an admixture of metal dust, for example of magnesium, aluminum or iron carried by oxygen gas. And, the third supply is for example pure oxygen or the like.
It is an object of this invention to shield the first mentioned pilot or igniter flame from extinguishment by the surrounding waters into which the torch is immersed. To this end a shield surrounding the torch is supplied with a fourth gas, air, which flows under pressure therefrom to exclude the intrusion of water into the combustion chamber within said shield. In practice, the shield is retractile so as to pass over obstructions projecting from the surface of the steel to be cut.
It is an object of this invention to retract the torch until it is in a position to perform the cutting operation. To this end retractile advancement means is employed to retractably place the torch in a cutting position.
The torch angle with respect to the wall to be cut will vary, depending upon the disposition of the wall to be cut. The cut steel has a tendancy to slough-off and blow back, as well as to drip downwardly. Therefore, when the cutting surface is inclined or vertical, the torch is preferably inclined so as to avoid the sloughing steel. In practice, the torch disposition will vary as circumstances require.
It is also an object of this invention to remotely control the position of the torch with respect to the cutting surface, after the torch has been placed in cutting position. In practice, when steel casing is to be cut, the torch is centered upon reaching the cutting position. As shown, retractile hydraulic means is provided to retractably center positioning legs that center the torch within the casing.
It is still another object of this invention to monitor and/or observe the progress of the cutting operation. To this end temperature probes and light probes are provided. For example, thermocouples sense the preheat temperature, and fiber optics sense the light intensity for visual observation. Also, closed circuit television can be employed.